Biology – Cell structures (B1.1)
The light microscope
KEY WORDS
Learning objectives: • •
magnification resolving power micrographs
observe plant and animal cells with a light microscope understand the limitations of light microscopy.
The type of microscope you have used in the school laboratory is called a light microscope. Microscopes produce a magnified image of the specimen you are looking at, making them look bigger than they are.
DID YOU KNOW?
eyepiece lenses
British scientist Robert Hooke first used the term ‘cell’. He recorded the first drawings of cells using a compound microscope in his book Micrographia, which was 350 years old in 2015.
objective lenses
stage
You may also have heard of Hooke for his law of elasticity, Hooke’s law, in physics.
lamp
Figure 1.1 A light microscope
Magnification The magnified image is produced by two lenses, an eyepiece and an objective lens. There is usually a choice of objective lenses.
1
Calculate is the total magnification with an eyepiece magnification of ×15 and an objective lens magnification of ×40?
2
What magnification would the objective lens need to be to give a total magnification of ×300 with an eyepiece of ×15?
Total magnification = magnification of eyepiece × magnification of objective lens For instance, if the eyepiece has a magnification of ten, which is written ×10, and the objective lens has a magnification of ×40, the total magnification is ×400.
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